Mr. Smith challenged his students to create an electromagnet that will pick up more paper clips than anyone else in the class. Timmy is very excited and begins to collect all of the necessary materials. He finds a D-cell battery, an iron nail, and a large roll of copper wire. What could Timmy do, using just these materials, to increase the strength of his electromagnet to pick up the maximum amount of paper clips?
A) cut the iron nail in half to use as the core
B) only attach the battery to one end of the nail
C) increase the number of coils of copper he puts around the nail
D) decrease the number of coils of copper wire he puts around the nail